#!/usr/bin/env python
# --*-- coding:utf-8 --*--
# author:g-y-b time:2020/6/17
import numpy as np

img = np.array(([1, 2, 3, 4], [5, 6, 7, 8], [1, 2, 3, 4], [5, 6, 7, 8]))
print(img)
a = 1
b = 2
print(img[::2, ::2])
print(a << 1)
print(a << 2)
print(a << 3)
print(b << 1)
print(b << 2)
print(b << 3)